The present invention relates to an apparatus for diagnosing vascular systems, such as a circulatory system of a blood vessel, in an organism, and more particularly, to the apparatus, having a combined function by an X-ray fluoroscopic system and an ultrasonic tomographic system with a catheter, for acquiring clinical information of circulatory illness by the combined function.
In recent diagnosis of circulatory illness, angiography by X-rays diagnostic systems has been in general use for the blood vessels ranging from the head to the legs of a patient. The angiography by X-rays provides a fluoroscopic image of the blood vessels on a display device. In a typical fashion, the fluoroscopy is effective in not only qualitative diagnosis by observing it but quantitative diagnosis by measuring internal diameters of the vessel imaged. The quantitative diagnosis includes a stenosis index, the rate in internal diameter between a selected non-illness portion and a selected illness portion along the vessel being imaged, whose figure is normally shown by quick calculation on the same display with the fluoroscopic image. The stenosis index can provide important information on whether treatment of the illness is required.
However, images supplied by the X-ray fluoroscopic system remains in two-dimensionally projected images from one direction, thus being impossible to recognize the three-dimensional blood vessel accurately. For example, when calculating a cross section of the blood vessel (the value of the cross section contributes to determining the stenosis index), the value is not always accurate. In addition, obscurity in resolution exists due to an X-ray focus size and scattered rays, which decrease in most cases the accuracy of various values determined from the projected image.
On the other hand, an ultrasonic tomographic system with a catheter also provides images usable for diagnosis of circulatory illness. In the ultrasonic tomographic system with the catheter inserted into a blood vessel, the system holds an ultrasonic probe at one end portion of the catheter. The ultrasonic probe transmits ultrasonic pulse signals almost perpendicularly toward the internal wall of the blood vessel and receives their echo signals at an inserted position, so that the echo signals will be processed to image data by an image processor. The image data thus-obtained creates on a display a real-time cross-sectional tomographic image of the blood vessel, covering from its lumen to wall portion. Hence, the cross sectional tomographic image can be used for finding an illness portion such as a stenosis in the vessel.
However, the image displayed by the above ultrasonic diagnostic system is always fixed to a view in the longitudinal direction of the vessel, and thus an operator is limited to observe only a cross sectional image perpendicularly to the vessel wall at the inserted position of the ultrasonic probe. As a result, it is difficult to visualize the structure of the whole vessel in one view, even though the internal diameter of the vessel may change with its longitudinal positions because of a stenosis. The operator can transfer the catheter many times to a quantity of diagnostic positions for viewing the whole structure. However, it is impossible to view the whole structure at one time and therefore results in long diagnostic time and difficulty in operation.